PHY Preamble Format for Wireless Communication System

ABSTRACT

A system and method of extracting data from data packets transmitted over a wireless network includes receiving a data packet having a preamble portion and a payload portion. The preamble portion is cross correlated with a first known spreading sequence to generate a first timing signal and the preamble portion is cross correlated with a second known spreading signal to generate a frame timing signal. An impulse is detected in the first timing signal and a first timing parameter is set based upon the detected impulse in the first timing signal. An impulse is detected in the frame timing signal and a frame timing parameter is set based upon the detected impulse in the frame timing signal. Data is extracted from the received payload portion according to the first timing parameter and the frame timing parameter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/751,388, filed on Jan. 28, 2013, which is a continuation of U.S. Pat.No. 8,385,390, filed on Apr. 7, 2009, which claims priority from U.S.Provisional Patent Application No. 61/053,526, filed on May 15, 2008,and entitled “PHY Preamble Format for 60 GHz Wideband WirelessCommunication Systems,” and from U.S. Provisional Patent Application No.61/078,925, filed on Jul. 8, 2008, and entitled “PHY Preamble Format for60 GHz Wideband Wireless Communication Systems,” the entirety of whichare incorporated herein by reference.

FIELD

The technology described in this patent document relates generally towireless data transmission and more particularly to physical level frameformats for wireless data transmission.

BACKGROUND

Wideband wireless systems operating at high frequencies, such as the 60GHz frequency range, are able to realize high data rate transmissions inthe order of Gigabits per second (Gbps). Wideband wireless systems areable to accomplish these high data rates through the use of very widechannel bandwidths because channel capacity (C) is proportional tochannel bandwidth (B) as illustrated in the Shannon-Hartleychannel-capacity theorem:

C=B*Log₂(1+S/N),

where S/N is the signal-to-noise power ratio. Because input datasequences tend to be narrowband in nature, to take advantage of the highdata-rate capabilities of wideband transmission, narrowband data signalsare combined with a noise-like, pseudo-random number sequence that isknown to both the transmitter and receiver to spread the data signalover a wide frequency band. The injection of such a “spreading sequence”enables high-speed transmission of the wideband data signals. Thewideband data signals are decoupled from the known spreading sequence atthe receiver, leaving the narrowband data signals for extraction.

FIG. 1 depicts a block diagram of a spread spectrum transmitter. Datasignals 32 are transmitted by an antenna 34 via a transmission chain 36.As described above, in order to spread the data signals 32 over a widefrequency band, a spreading sequence provided by a spreading sequencegenerator 38 is combined with the data signals 32 at some point in thetransmission chain 36 to produce a wideband signal to be transmitted viathe antenna 34.

Different spread-spectrum techniques are distinguished according to thepoint in the transmission chain at which a spreading sequence isinserted in the communication channel. FIG. 2 depicts a block diagram ofa system for injecting a spreading sequence at different points in atransmission chain. In FIG. 2, data 42 is transmitted by an antenna 44via a modulator chain 46 and a power amplifier 48. If the spreadingsequence is inserted at the data level, as shown at 50, the spectrumspreading is referred to as a direct sequence spread spectrum technique(DSSS). The modulation chain 46 receives the data 42 and a signal from alocal oscillator 52. If the spreading sequence is incorporated at thecarrier-frequency level, as shown at 54, the spectrum spreading isreferred to as a frequency hopping spread spectrum technique (FHSS).Further, if the spreading sequence acts as an on/off gate to thetransmitted signal at the power amplifier 48, as shown at 56, thespectrum spreading may be referred to as a time hopping spread spectrumtechnique (THSS).

A wideband signal may be transmitted as a single carrier signal or amultiple carrier signal, such as an orthogonal frequency-divisionmultiplexing (OFDM) signal. Both single carrier and multiple carriertransmissions may implement the same basic packet format structure shownin FIG. 3. The packet 60 begins with a preamble portion 62 that providestraining information to help receiver setup. The preamble portion mayinclude data to assist the receiver: detect the current packet, adjustautomatic gain control (AGC) settings, perform frequency and timingsynchronizations, set a single carrier/multiple carrier parameter, set aheader rate parameter, set a network ID number parameter, set a piconetID number parameter, as well as setting other setup parameter. A headerportion 64 provides information regarding parameters for decoding thepacket payload portion 66 such that the receiver may adjust its decodingapparatus accordingly. The header portion 64 may include data regardingthe length of the payload portion, modulation and coding methods, aswell as other parameter data. The payload portion 66 contains the datasought to be transmitted from the transmitter to the receiver.

FIG. 4 depicts an example packet preamble format. A packet preamble 70may include a packet synchronization sequence (SYNC) 72 that may be usedfor determining the start of the packet, frequency/timingsynchronization, AGC setting, and other parameter transmission. A startframe delimiter (SFD) 74 may be included in the preamble as a timingreference for the remainder of the packet as well as transmission ofother parameters. The channel estimation sequence (CES) 76 may beincluded for use in channel estimation at the receiver.

FIG. 5 depicts an example packet structure in the form of an 802.15.3ccompliant single carrier frame specification. As noted above, the packetbegins with a preamble portion 80 that includes a SYNC segment 82, anSFD segment 84, and a CES segment 86. A frame header portion 88 followsthe preamble portion 80, and the frame header 88 is followed by apayload portion 90.

FIG. 6 depicts an example multiple carrier 802.15.3c OFDM frame format.It is noted that the time scale in FIG. 6 runs from right-to-left asindicated at 102. The OFDM packet begins with a preamble portion 104that includes a SYNC segment 106, an SFD segment 108, and a CES segment110. The preamble portion 104 is followed by a frame header portion 112that precedes a data payload portion 114.

As described above, narrowband data signals are often spread over a widebandwidth to take advantage of increased channel capacity available towideband signals. FIG. 7 depicts an example spreading sequence and covercode plan for a preamble portion of a packet. The depicted preambleportion includes a SYNC segment 118 and an SFD segment 120. The SYNCsegment 118 includes data signals combined with a spreading sequence 122denoted as ‘a.’ Data is transmitted during the SYNC segment 118 in theform of a repeated cover code 124 that is combined with the spreadingsequence, ‘a’ 122, to generate the wideband data signal. The repeatedSYNC cover code 124 may include data instructing the receiver as tofrequency/timing synchronization, AGC setting, as well as otherparameters.

The SFD segment 120 may be transmitted using the same spreadingsequence, ‘a,’ as is used for the SYNC segment 118 as noted at 126. TheSFD segment 120 may include data conveyed via a cover code 128 that iscombined with the spreading sequence 126 to generate the wideband datasignal. The first segment of the SFD cover code 128 may be selected soas to generate a large phase shift between the last SYNC cover codesegment and the first SFD cover code segment. This large phase shift maybe detected by a receiver to identify a transition between the SYNC 118and SFD 120 segments, and the large detected phase shift may be used asa timing reference for the remainder of the packet. Other data,including the length of the CES segment, may be transmitted via the SFDsegment cover code 128.

SUMMARY

In accordance with the systems and methods described herein, a systemand method of extracting data from data packets transmitted over awireless network may include receiving a data packet having a preambleportion and a payload portion. The system may further include crosscorrelating the preamble portion with a first known spreading sequenceto generate a first timing signal and cross correlating the preambleportion with a second known spreading signal to generate a frame timingsignal. An impulse may be detected in the first timing signal and afirst timing parameter may be set based upon the detected impulse in thefirst timing signal. An impulse may be detected in the frame timingsignal and a frame timing parameter may be set based upon the detectedimpulse in the frame timing signal. Data may be extracted from thereceived payload portion according to the first timing parameter and theframe timing parameter.

The system may further be characterized by a first portion of thepreamble portion that is transmitted with the first known spreadingsequence corresponding with a synchronization segment of the preambleportion and a second portion of the preamble portion transmitted withthe second known spreading sequence corresponding with a start framedelimiter segment of the preamble portion. A parameter other than theframe timing parameter may be set using a cover code transmitted duringa first iteration of the second known spreading sequence at thebeginning of the start frame delimiter setting.

A first cover code may be repeated throughout the synchronizationsegment, where a second cover code is repeated twice at the beginning ofthe start frame delimiter segment, where the second cover code iscomplementary to the first cover code. One or more parameters other thanthe frame timing parameter may be extracted from cover codes transmittedwith the second known spreading sequence following the twice repeatedsecond cover code. The first known spreading sequence may be a firstGolay sequence and a second known spreading sequence may be a secondGolay sequence that is complementary to the first Golay sequence. One ormore physical layer parameters may be extracted from cover codestransmitted with the first known spreading sequence or the second knownspreading sequence in the preamble portion.

As a further example, a method of extracting data from a received datapacket may include receiving a preamble portion and a payload portion ofthe received data packet. The received preamble portion may be crosscorrelated with a first known spreading sequence to generate a firsttiming signal and the received preamble portion may be cross correlatedwith a second known spreading signal to generate a second timing signal.Impulses may be detected in both the first and second timing signals. Afirst timing parameter may be set based upon a first in time detectedimpulse in either the first timing signal or the second timing signal. Aframe timing parameter may be set based upon a detected impulse in thesecond timing signal if an impulse from the first timing signal is usedto set the first timing parameter, or a frame timing parameter may beset based upon a detected impulse in the first timing signal if animpulse from the second timing signal is used to set the first timingparameter. A third parameter may be set based upon which timing signalproduces the first in time impulse, and data may be extracted from thereceived payload portion according to the set first timing parameter,the set frame timing parameter, and the third parameter.

As an additional example, a wireless receiver configured to extract datafrom data packets may include an antenna for receiving a data packethaving a preamble portion and a payload portion. A firstcross-correlator may be configured to cross correlate the preambleportion with a first known spreading sequence to generate a symboltiming signal, and a second cross-correlator may be configured to crosscorrelate the preamble portion with a second known spreading sequence togenerate a frame timing signal. A first impulse detector may detect animpulse in the symbol timing signal, and a parameter setter may set asymbol timing parameter based upon the detected impulse in the symboltiming signal by the first impulse detector. A second impulse detectormay be configured to detect an impulse in the frame timing signal, wherethe parameter setter is configured to set a frame timing parameter basedupon the detected impulse in the frame timing signal by the secondimpulse detector. A data extractor configured to extract data from thereceived payload portion according to the set symbol timing parameterand the set frame timing parameter.

The receiver may further be characterized by a first portion of thepreamble portion that is transmitted with the first known spreadingsequence corresponding with a synchronization segment of the preambleportion and a second portion of the preamble portion transmitted withthe second known spreading sequence corresponding with a start framedelimiter segment of the preamble portion. A parameter other than theframe timing parameter may be set using a cover code transmitted duringa first iteration of the second known spreading sequence at thebeginning of the start frame delimiter setting.

A first cover code may be repeated throughout the synchronizationsegment, where a second cover code is repeated twice at the beginning ofthe start frame delimiter segment, where the second cover code iscomplementary to the first cover code. One or more parameters other thanthe frame timing parameter may be extracted from cover codes transmittedwith the second known spreading sequence following the twice repeatedsecond cover code. The first known spreading sequence may be a firstGolay sequence and a second known spreading sequence may be a secondGolay sequence that is complementary to the first Golay sequence. One ormore physical layer parameters may be extracted from cover codestransmitted with the first known spreading sequence or the second knownspreading sequence in the preamble portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a block diagram of a spread spectrum transmitter.

FIG. 2 depicts a block diagram of a system for injecting a spreadingsequence at different points in a transmission chain.

FIG. 3 depicts an example packet format.

FIG. 4 depicts an example packet preamble format.

FIG. 5 depicts an 802.15.3c single carrier frame format.

FIG. 6 depicts an 802.15.3c OFDM frame format.

FIG. 7 depicts an example spreading sequence and cover code plan for apreamble portion of a packet.

FIG. 8 depicts an example spreading sequence and cover code plan for apreamble portion of a packet having different spreading sequences forthe SYNC and SFD segments.

FIG. 9 depicts example cross correlation results for a packet usingdifferent spreading sequences for the SYNC and SFD segments.

FIG. 10 depicts a block diagram of a receiver.

FIG. 11 depicts a block diagram illustrating components of a timingdetector in detail.

FIG. 12 depicts an example spreading sequence and cover code plan for apreamble portion of a packet having a complementary cover codetransmitted in the first two slots of an SFD segment.

FIG. 13 depicts an example spreading sequence and cover code plan for apreamble portion of a packet having different spreading sequences forthe SYNC and SFD segments and a complementary cover code transmitted inthe first two slots of the SFD segment.

FIG. 14 depicts a flow diagram illustrating a process for extractingdata from a received data packet transmitted over a wireless network.

FIG. 15 depicts a flow diagram illustrating another process forextracting data from a received data packet transmitted over a wirelessnetwork.

DETAILED DESCRIPTION

Use of the frame format for the SYNC and SFD segments described withreference to FIG. 7, which uses differing cover codes to differentiatebetween the SYNC and SFD segments, may result in difficulty in detectingthe SYNC/SFD boundary, which identifies the frame timing reference, inreceivers suffering from low sensitivity. At the SYNC/SFD boundary, areceiver may use either a coherent or noncoherent method to determinethe start of the SFD segment and establish frame timing.

The coherent method performs channel estimation based on the signals ofthe SYNC portion of the preamble. The coherent method may be performedin an adaptive fashion. However, the SYNC segment may be too short forthe channel estimation adaptation to converge to a reliable value.Implementation of the coherent method is complicated and performance maynot be guaranteed.

The noncoherent method of detecting the SYNC/SFD boundary is not basedon channel estimation and therefore, may be less complicated. However,the noncoherent method may have a low sensitivity, meaning that insuboptimal conditions such as in systems having a low signal-to-noiseratio (SNR), a high delay spread channel, or a carrier frequency offset,the frame timing accuracy may be poor. Because frame timing based ondetection of the SYNC/SFD boundary is important to proper receipt of anentire packet, low sensitivity may limit performance.

FIG. 8 depicts an example spreading sequence and cover code plan for apreamble portion of a packet having different spreading sequences forthe SYNC and SFD segments. The depicted preamble portion includes a SYNCsegment 132 and an SFD segment 134. The SYNC segment 132 utilizes afirst spreading sequence, ‘a’ 136, that is combined with a cover codeset 138 carrying packet configuration data such as AGC settings. TheSYNC segment 132 is followed by the SFD segment 134 that is transmittedusing a second spreading sequence, denoted as ‘b’ 140, which is combinedwith a set of parameter carrying SFD cover codes 142. Each of thespreading sequences, ‘a’ 136 and ‘b’ 140, are known to both thetransmitter and the receiver. The use of different spreading sequencesfor the SYNC and SFD segments enables a noncoherent frame timingmechanism to be utilized for SYNC/SFD boundary detection at a receiverthat may be less susceptible to low sensitivity than previous methods.Additionally, the use of the spreading sequence transition to identifythe SYNC/SFD boundary frees the first cover code of the SFD segment formeaningful parameter transmission.

Because both of the utilized spreading sequences are known to thetransmitter and the receiver, in a system using the preamble frameformat described with reference to FIG. 8, the SYNC/SFD boundary may bedetected utilizing a cross correlation technique. More specifically,cross correlating a received signal with a known spreading signal willproduce an impulse at the beginning of each repetition of that spreadingsequence in the received signal. By detecting such impulses, thebeginning of a frame and the SYNC/SFD boundary may be identified. Forexample, a cross correlation such as:

${C_{1}(n)} = {{\sum\limits_{k = 0}^{N - 1}{{a^{*}(k)}{r\left( {n + k} \right)}}}}$

may be utilized, where ‘a’ is the known SYNC spreading sequence, ‘r’ isthe received signal, and ‘N’ is the length of the ‘a’ spreadingsequence. A similar cross correlation, such as:

${C_{2}(n)} = {{\sum\limits_{k = 0}^{M - 1}{{b^{*}(k)}{r\left( {n + k} \right)}}}}$

may be utilized to detect the beginning of each SFD spreading sequencerepetition, where ‘b’ is the known SFD spreading sequence, ‘r’ is thereceived signal, and ‘M’ is the length of the ‘b’ spreading sequence. If‘a’ and ‘b’ are selected spreading sequences having good auto and crosscorrelation properties, then the periodic cross correlation between ‘a’and ‘b’ will be close to zero while the aperiodic/periodic autocorrelation will result in a narrow main lobe and a low level side lobe.Thus, the beginning of a packet may be identified by detecting impulsesin the C₁ signal, and the SYNC/SFD boundary may be identified bydetecting impulses in the C₂ signal. Selection of a pair ofcomplementary Golay spreading sequences may enable these results.

FIG. 9 depicts example cross correlation results for a packet usingdifferent spreading sequences for the SYNC and SFD segments. Theillustrated preamble portion shows a SYNC segment 152 and an SFD segment154, where the SYNC segment 152 is transmitted using a first spreadingsequence, ‘a’ 156, and the SFD segment 154 is transmitted using a secondspreading sequence, ‘b’ 158. The SYNC 152 and SFD 154 segments may carryother parameter data in their respective cover codes 160, 162. The twographs of FIG. 9 depict cross correlations using the above describedformulas in a low delay spread channel system having an SNR of ˜10 dBusing complementary Golay spreading sequences. As illustrated at 164,the beginning of each ‘a’ spreading sequence 156 is marked by an impulse164 in the C₁ signal depicting a cross correlation of the receivedsignal and the ‘a’ spreading sequence. As shown at 166, the beginning ofeach ‘b’ spreading sequence 158 is marked by an impulse 166 in the C₂signal depicting the cross correlation of the received signal and theknown ‘b’ spreading sequence. Thus, the beginning of the packet may beidentified by detecting the first C₁ impulse 164, and the SYNC/SFDboundary may be identified by detecting the first C₂ impulse 166.

FIG. 10 depicts a block diagram of an example receiver configured todetect the start of a packet and the SYNC/SFD boundary using the abovedescribed cross correlation technique. The receiver 170 receives awirelessly transmitted signal via an antenna 172. The received signal ispropagated to both a timing detector 174 and a data extractor 176. Thetiming detector 174 identifies the start of the packet, the SYNC/SFDboundary for frame timing, and may identify other transmittedparameters. The timing detector 174 propagates these timing and othersetup parameters to the data extractor 176 for proper extraction of thetransmitted payload data.

FIG. 11 depicts a block diagram illustrating components of an exemplarytiming detector in detail. The receiver 180 receives a wirelesslytransmitted data signal via an antenna 182. The received signal ispropagated to both a timing detector 184 and a data extractor 186. Thereceived signal is passed within the timing detector 184 to a firstcross correlator 186 and a second cross correlator 188. The first crosscorrelator 186 also receives a first known spreading sequence 190, andthe second cross correlator 188 further receives a second knownspreading sequence 192. The first cross correlator 186 cross correlatesthe received signal with the first known spreading sequence 190 togenerate a symbol timing signal. A first impulse detector 194 detectsimpulses in the symbol timing signal and alerts the parameter setter 196to identify the start of a packet. The second cross correlator 188 crosscorrelates the received signal with the second known spreading sequence192 to generate a frame timing signal. A second impulse detector 198detects impulses in the frame timing signal and alerts the parametersetter 196 to set the frame timing reference. These timing signals aswell as any other packet handling/decoding parameters identified by thetiming detector 184 are passed from the parameter setter 196 to the dataextractor 186 for use in extracting payload data. A cover code decoder300 is configured to extract one or more physical layer parameters fromcover codes transmitted with the first known spreading sequence or thesecond known spreading sequence in the preamble portion.

The above described framework may be extended such that the spreadingsequence transition may identify additional PHY/MAC parameters beyondthe SYNC/SFD boundary frame timing. For example, the beginning of apacket may be identified by detection of an impulse in either of the C₁cross correlation of a received signal with a first spreading sequenceor the C₂ cross correlation with a second spreading sequence. TheSYNC/SFD boundary frame timing may then be identified by an impulse inthe other cross correlation signal that was not used to identify thestart of a packet. Meaningful parameter data may then be determined fromthe order in which the spreading sequences were used. For example, ifthe ‘a’ spreading sequence was used in the SYNC segment and the ‘b’spreading sequence was transmitted with the SFD segment, then a singlecarrier payload portion may be forthcoming. Alternatively, if the ‘b’spreading sequence was transmitted with the SYNC segment and the SFDsegment was sent using the ‘a’ spreading sequence, then an OFDM payloadportion may follow.

Further, more than two spreading sequences may be utilized, requiringfurther cross correlators in the receiver. The first impulse detected ina cross correlator would mark the start of a packet, and the firstimpulse in a different cross correlator would mark the SYNC/SFDboundary. The two spreading sequences identified as having caused thecross correlation impulses and their order could identify one or moreparameters of the incoming signal. Additionally, cover codes may stillbe utilized to transmit parameter data.

FIG. 12 depicts an example spreading sequence and cover code plan for apreamble portion of a packet having a complementary cover codetransmitted in the first two slots of the SFD segment. The depictedpreamble portion illustrates a SYNC segment 202 and an SFD segment 204.The example SYNC segment 202 is transmitted using a first spreadingsequence, ‘a’ 206, and carries a SYNC cover code 208 that is a constantvalue of ‘1’ as identified at 210. The SFD segment 204 is alsotransmitted using the ‘a’ spreading sequence as shown at 214. The SFDsegment cover code 212 includes a ‘−1’ value for the first two segmentportions as shown at 216 and may include other cover code values thatconvey meaningful parameter data as shown at 218. The SYNC cover codecould be set to a value other than 1. However, all of the SYNC covercodes of this example are the same, and the first two cover codeportions of the SFD segment are complementary to the SYNC cover codevalue.

The packet preamble configuration of FIG. 12 may be advantageous insystems that suffer from low sensitivity, which may have difficultyidentifying the SYNC/SFD boundary for frame timing. The use of two SFDsegment cover code portions that are complementary to the SYNC segmentcover code portion 208 may aid in detection of the SYNC/SFD boundary bymaintaining the large phase shift between the last cover code of theSYNC segment and the first cover code portion of the SFD segment for alonger period of time.

FIG. 13 depicts an example spreading sequence and cover code plan for apreamble portion of a packet having different spreading sequences forthe SYNC and SFD segments and a complementary cover code transmitted inthe first two portions of the SFD segment. This packet preamble formatcombines the advantages described with reference to FIG. 12 with thebenefits of the use of different spreading sequences for the SYNC andSFD segments. FIG. 13 depicts a SYNC segment 222 and an SFD segment 224.The SYNC segment 222 is transmitted using a spreading sequence, ‘a’ 226,and carries cover codes 228 that repeat a value, such as ‘1,’ for allportions of the SYNC segment 222. The SFD segment 224 is transmittedusing a second spreading sequence, ‘b’ 234. The first two portions ofthe cover codes 232 of the SFD segment 224 are complementary to therepeated SYNC cover code 228 as identified by the ‘−1s’ at 236. Theremaining cover codes 238 of the SFD segment 224 may be used to transmitother meaningful parameter data. A receiver receiving a packet havingthe preamble format shown in FIG. 13 may use either or both of thediffering spreading sequences and complementary cover codes to identifythe SYNC/SFD boundary for frame timing. The use of both identifiers mayimprove boundary identification, resulting in better performancecapabilities over the use of one of the individual identifiers alone.

FIG. 14 depicts a flow diagram illustrating a process for extractingdata from a received data packet transmitted over a wireless network. Acomputer-implemented method of extracting data from a received datapacket transmitted over a wireless network may receive a preambleportion and a payload portion of the received data packet as shown at242. The received preamble portion may be cross correlated with a firstknown spreading sequence, as shown at 244, to generate a symbol timingsignal, and the received preamble portion may be cross correlated with asecond known spreading sequence, as shown at 246, to generate a frametiming signal. An impulse may be detected in the symbol timing signal,as shown at 248, and a symbol timing parameter may be set based upon theimpulse detection in the symbol timing signal at 250. At 252, an impulsemay be detected in the frame timing signal, and a frame timing parametermay be set based upon the detection of an impulse in the frame timingsignal at 254. Data may be extracted from the received payload portionaccording to the set symbol timing parameter and frame timing parameter,as shown at 256.

FIG. 15 depicts a flow diagram illustrating another process forextracting data from a received data packet transmitted over a wirelessnetwork. A computer-implemented method of extracting data from areceived data packet may include receiving a preamble portion and apayload portion of the received data packet, as shown at 262. At 264,the received preamble portion may be cross correlated with a first knownspreading sequence to generate a first timing signal, and at 266, thereceived preamble portion may be cross correlated with a second knownspreading signal to generate a second timing signal. A first impulse isdetected in one of the first or second timing signals at 268, and asymbol timing parameter is set based on the first impulse detection at270. At 272, an impulse is detected in the other timing signal, and aframe timing parameter is set based on the other impulse detection at274. At 276, a third parameter is set based on the order of theimpulses. Data is extracted from the payload portion of the packet at278 according to the timing and the third parameters.

This written description uses examples to disclose the invention,including the best mode, and also to enable a person skilled in the artto make and use the invention. It should be noted that the systems andmethods described herein may be equally applicable to otherconfigurations. For example, the proposed frame format, transmitters,and receivers may be extended for other wireless systems that are notconstrained to 60 GHz systems such as future WLAN systems, WiMax, WPAN,cellular systems, etc. The system may also include a computer-readablememory configured to store extracted data. The patentable scope of theinvention may include other examples that occur to those skilled in theart.

It is claimed:
 1. A method of extracting data from data packetstransmitted over a wireless network, comprising: receiving a datapacket, the data packet having a preamble portion and a payload portion;cross correlating the preamble portion with a first known spreadingsequence to generate a first timing signal; cross correlating thepreamble portion with a second known spreading signal to generate aframe timing signal; detecting an impulse in the first timing signal;setting a first timing parameter based upon the detected impulse in thefirst timing signal; detecting an impulse in the frame timing signal;setting a frame timing parameter based upon the detected impulse in theframe timing signal; and extracting data from the received payloadportion according to the set first timing parameter and the set frametiming parameter.